First incident is something that looks like another window appearing under the taskbar. The size of this thing grew till it hid the taskbar and I moved the taskbar to the top of the screen. After a while, another flickering line appeard and the screen is unstable. I formated the c:\ partitian and reinstalled windows again, but the problem still persists. Is this a software or a hardware problem? Is it possible that it still persists because I didn't format the d:\ partitian too?

Re: The display screen is unstable and there are two lines in the upper and lower ends of the screen

Start immediately tapping the f10 key on boot up to get into the BIOS, if the problem shows up there, then it is a hardware problem.

Connect up an external monitor, if the image is good on the monitor then the screen or the cable is bad. If the image is the same on the external monitor then the video card is gone or more common, the solder has failed which holds it to the mother board.